Thank you for your response, but I found out that the problem is solved much more simply.
When I bought my phoneI I used Smart Switch to transfer my apps. After doing so, I wanted to keep some of those apps in the Secure Folder so added them there. This resulted in some apps appearing in the Secure Folder--their app icons had a lock in the lower right corner. However there was still a copy of the app in the regular app folder. When this happens, the S8 acts as if these are different apps and when a message comes in on the app, it's posted twice--once from each app. And it can also have two windows of the app open at the same time.
THE SOLUTION is to go into the main app folder (not the Secure Folder) and uninstall the app. You will be left with only one copy of the app in the Secure Folder.
This is not a proper solution and the problem is not resolved. Please reopen the inquiry!
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